Mayor Johnson has sailed into a big new week with a with strong sea breeze at his rear. On Wednesday he'll be publicly grilled about his first budget, which might come as light relief from any power-grappling with Jacqui Smith over who gets to be the next boss of the Met. But no matter how squally the political weather becomes, he'll have the PR triumph of last Friday's "Boris Island" jaunt to keep him warm.

"It's going to happen, I just know it," enthused his deputy Kit Malthouse, when we spoke on the phone that evening. Malthouse has, as he puts it, "brought to prominence" anew the old idea of a whole new airport in the Thames Estuary and was among those on the dredger Brabo inspecting the proposed location. On learning of the nasty weather I'd texted him, asking if anyone had thrown up. I got no response to that, but his later reply informed me that the sea was "full of clobber."

What kind of clobber? He spoke of "World War 2 artillery batteries sticking out of the water like tripods," and "a test island" built when Maplin Sands, a previous estuary airport idea, was under consideration. There was even a bit of sunken ship breaking the surface, which "indicates a depth of between four and 17 metres," he said. All good signs, Malthouse explained: the shallowness would make the engineering easier and the "clobber" showed that this stretch of water is far from environmentally unspoiled. As for the eyesore factor, he assured me that both the Kent and Essex coastlines were mere "thin lines" in the distance.

Is Team Boris really serious about this wheeze? I'd say, yes. It speaks to a Tory taste for entreprenurial high adventure, and now they've Crossrail boss Doug Oakervee saying "piece of cake" (well, almost), support from Labour MPs, a diagram in the Evening Standard and everything. Also, it allows Boris to do a part of the mayor's job that suits one of his strengths, which is having a wizard idea and drawing a crowd to watch him enthuse. Only LBC and BBC London had a press presence on the boat, but the story got plenty of coverage, including from me. The Blond is pure box office.

Scepticism has yet to melt away, though. Transport expert Tom at Boris Watch not only tracked the voyage of the Brabo but is also developing a detailed critique of the entire scheme. See here and here and here. His verdict:

This bizarre proposal is best seen as an attempt by Boris to be seen as the principle opponent of the Third Runway, by spin and PR rather than actual campaigning. He'd have been better off coming to Pro London yesterday, where he'd have found a lot of people perfectly willing to oppose it, but without having to invent airport schemes consisting of 90% BS and spin.

Still, "greenwash" publicity exercise or not the mayor and his men give very impression of believing in it and, for now, it's not doing them any harm.